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    <title>Document</title>

    <script>
        var year = prompt("输入年份，判断闰年还是平年。")
        if ((year % 4 == 0 && year % 100 != 0) || (year % 400 == 0)) {
            alert("它是闰年");
        } else {
            alert("它是平年");

        }



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